I know the Mark 2 Chieftain tanks came out in the 1960's, but I wondered if they came in Deep Bronze Green, as I thought the green and black was of a later era.

Mark 2 - definitely gloss Deep Bronze Green when new. I couldn't say the same for the Mark 3 though; a bit borderline between the old DBG era and the replacement NATO Green and Black, hence not the same green - a matt finish, formulated to reflect Infra Red light. The references I have say early 1970s introduction.